This invention relates generally to field emission structures, such as those used in vacuum microelectronic devices and more particularly concerns fabrication methods for making the field emission structure.
Field emission structures have been used in a variety of devices including vacuum micro tubes (W. J. Orvis et al "Modeling and Fabricating Micro-Cavity Integrated Vacuum Tubes", IEEE Transactions on Electron Devices, Vol. 36. no. 11. November 1989). These elements can be made in a variety of ways. In a paper by Yao, Arney, and MacDonald in the Journal of Microelectromechanical systems, vol. 1, no. 1, March 1992 titled Fabrication of High Frequency Two-Dimensional Nanoactuators for Scanned Probe Devices a two-dimensional field emission structure is made by following the process steps of:
A) depositing an oxide-nitride-oxide stack on a substrate and an aluminum mask on the stack,
B) etching the stack and the substrate to form a protruding structure,
C) depositing a sidewall mask on the protruding structure,
D) performing an isotropic recess etch to form an undercut structure in the protruding structure and to start forming the field emission structure,
E) performing an isolation oxidation to finish forming the field emission structure,
F) removing the oxidation to release the structure.
This process results in a pair of conical tips that can be used in scanned probe devices. This process is cumbersome because it uses many complex steps to form the pair of complex tips and because some of the steps, such as the isotropic recess etch are difficult to control and reproduce with accuracy.